This invention relates generally to shutter mechanisms and, more particularly, to a rotary shutter mechanism for use in a photometric printing system.
Various shutter mechanisms are employed in photometric printing systems of the type used, for example, in the semiconductor industry to photometrically print an image of a photomask or a reticle on a semiconductive wafer by exposing selected regions of a photosensitive film on the semiconductive wafer to exposure light passing through the photomask or the reticle. In order to photometrically print this image on the semiconductive wafer with high resolution, it is very important to uniformly illuminate the photomask or the reticle and, hence, the selected regions of the photosensitive film on the semiconductive wafer with the exposure light. The shutter mechanisms conventionally employed in such photometric printing systems control the exposure period, but typically do not open all portions of the shutter aperture for the same length of time. Thus, the photomask or the reticle and, hence, the selected regions of the photosensitive film on the semiconductive wafer are therefore typically not uniformly illuminated with the exposure light. In addition to this important drawback, the shutter mechanisms conventionally employed in such photometric printing systems are typically larger and slower than desired for many photometric printing applications.